Abstract
Microporous poly(vinylidene fluoride-co-hexafluoropropylene) membranes were prepared by phase separation with supercritical CO 2 as non-solvent. The dry flat membranes were directly obtained after CO 2 pressure was diminished without post-treatment. Effects of experimental conditions such as the CO 2 pressure, the polymer concentration and the temperature on the membrane porosity and average pore size were investigated. It was found that these membranes have a “sponge-like” and asymmetric structure. The average pore size increases with increasing CO 2 pressure and temperature, but decreases with increasing polymer concentration. The porosity can reach approximately 88% and the average pore size was 5 μm or so. The crystallinity and thermal stability of membranes were characterized by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results showed that the membranes are α crystals with excellent thermal stability.
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